Regeneron Says Antibody Therapy Prevents COVID-19 Infections

Regeneron Pharmaceuticals is planning to ask the Food and Drug Administration (FDA) to allow its antibody cocktail to be used as a preventive treatment for COVID-19, the company said Monday.

New results from a clinical trial conducted with the National Institute of Allergy and Infectious Diseases found the drug reduced the risk of symptomatic infection by 81 percent in people who were not infected at the start of the trial, Regeneron said.

The company has already received emergency use authorization from the FDA to use its antibody drugs to treat adults with mild to moderate COVID-19 and pediatric patients at least 12 years old who have tested positive for the virus and are at high risk of severe disease but are not yet hospitalized.

The trial enrolled 1,505 people who were not infected with the virus but lived in the same household as someone who recently tested positive. The patients were randomized to receive either one dose of the antibody therapy or a placebo administered as injections.

After 29 days, 11 people out of the 753 who received a single 1,200 mg dose of the treatment developed symptomatic COVID-19; 59 people who received a placebo out of 752 participants developed symptomatic COVID-19.

The drug provided 72 percent protection against symptomatic infections in the first week and 93 percent protection in subsequent weeks, Regeneron said. The data has not yet been peer reviewed or published.

Regeneron also said the trial found individuals treated with the therapy who experienced a symptomatic infection resolved their symptoms in one week, compared to three weeks with placebo. Infected individuals also cleared the virus faster with the therapy, the company said.

Adverse events occurred in 20 percent of patients who received the antibody drug and 29 percent of those who received a placebo, Regeneron said, but nobody withdrew from the trial because of them.

None of the participants who received the therapy were hospitalized or went to the ER because of COVID-19 over the course of 29 days; four in the placebo group did so. There were four deaths in the trial — two in the therapy group and two in the placebo group — but none were reported due to COVID-19 or the drug.

“With more than 60,000 Americans continuing to be diagnosed with COVID-19 every day, the REGEN-COV antibody cocktail may help provide immediate protection to unvaccinated people who are exposed to the virus, and we are also working to understand its potential to provide ongoing protection for immunocompromised patients who may not respond well to vaccines,” George Yancopoulos, president and chief scientific officer at Regeneron, said in a statement.

The trial tested the antibody treatment for use as a “passive vaccine,” which involves directly injecting antibodies into the body. Traditional vaccines rely on a person’s immune system to activate and develop its own antibodies.

That means the treatment may provide immediate benefits, in contrast to active vaccines, which take weeks to provide protection. In addition, using injections rather than an infusion could make administering it more convenient than the currently authorized use for antibody drugs.

While much of the attention has been focused on vaccines, experts say therapeutic treatments are just as important to ending the pandemic, which has killed more than 562,000 Americans.

Source: Regeneron says antibody therapy prevents COVID-19 infections | TheHill

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Why Do Antibodies Fade After a COVID-19 Infection & Will The Same Thing Happen With Vaccines

Plasma cells secreting antibodies

The goal of the COVID-19 vaccines being rolled out worldwide is to stimulate our immune systems into creating a protective response against the coronavirus, particularly by generating antibodies. These antibodies then circulate in our blood until needed in the future, attacking and removing the coronavirus quickly from our bodies if we become infected.

The speed with which the scientific and medical communities have developed and tested these new vaccines has been extraordinary. However, this short timescale leaves us with some outstanding questions.

Key among these is how long the protection we receive from vaccination, or indeed from infection with the virus itself, will last. We know, for example, that antibody levels drop quite quickly following a COVID-19 infection.

How the immune system remembers

Our body’s remarkable ability to remember past encounters with infectious microorganisms and retain robust defences against them is due to the phenomenon of immunological memory. This memory resides in white blood cells known as lymphocytes, of which there are two main types: T cells and B cells.

When the body faces a new challenge – either a new infection or vaccine – specific T cells and B cells are recruited to deal with it. “Memory” versions of these specific cells are then kept on standby in case the same issue is encountered again in the future.

It is these B cells that are responsible for releasing antibodies into the blood. When an infection or vaccination occurs, some of them will metamorphose into specialised antibody-production factories, known as plasma cells.

Antibodies are proteins, and like any other protein will be naturally broken down and removed from the body within a few months at most. This is the reason why protection from antibodies that we receive passively, for example from our mothers in the womb or through breast milk, does not last very long. For longer-term protection, we need to produce antibodies for ourselves.

Our body’s ability to maintain antibody levels following infection or vaccination is a result of two mechanisms. In the early stages, if memory B cells detect any persistent infection or vaccine, some will continue to turn into new antibody-producing plasma cells.

Once the infection or vaccine has been completely removed, memory B cells no longer replenish the plasma cell population, which declines. However, some may persist as long-lived plasma cells (LLPCs), which can live for many years in our bone marrow, continually manufacturing and releasing large quantities of antibodies. LLPCs aren’t always created after an infection, but if they are, antibodies against a specific infection can be found in the blood for a long time after the infection has cleared.

Although we don’t yet fully understand which immunisation conditions are best for generating LLPCs, their presence has been linked to certain locations. For example, a US group discovered that LLPCs appear to prefer the marrow of certain bones above others. Ten years after tetanus vaccination, LLPCs were found in femur, humerus and tibia bone marrow much more commonly than that of the ribs, radius, vertebrae or iliac crest.

Quite why LLPCs prefer the marrow of these bones is not yet clear. One interesting possibility is differences in the bone marrow fat level. LLPCs were found to be surrounded by large numbers of fat cells in these bones. This suggests that it may be bone marrow fat content that affects the ability of LLPCs to move to – and reside long term in – certain bones.

But if LLPCs aren’t created, that doesn’t mean someone cannot generate more antibodies against a threat if it is encountered again in the future. Providing the person has generated memory B cells, these will recognise the familiar threat, and once again some will start transforming into new plasma cells, to begin antibody production once more.

Vaccine type affects durability too

There are many reasons why vaccination or infection do not always provide protection that is long lasting. Some of this is due to individual variation in our response to a given vaccine. However, the features of vaccines themselves determine the nature of the antibody response too.

One study found that although a greater proportion of individuals who received tetanus and diphtheria vaccines developed protective antibodies, these antibodies faded more rapidly than those generated by measles, mumps or smallpox vaccines. The key difference between these vaccines is that those against tetanus and diphtheria contain only isolated proteins (modified versions of the toxins that tetanus and diphtheria bacteria make), whereas the measles, mumps and smallpox vaccines contain live, weakened versions of these viruses.

Some people may not produce good responses to live vaccines due to pre-existing immunity to the vaccine itself, having already had a natural infection. However, those that do respond well tend to keep their responses for longer. This is partly due to persistence of the live vaccine in the body, which encourages the short-term replenishment of plasma cells. It is also likely that live vaccines are better at producing LLPCs.

We have already seen that the rate at which antibodies decay following COVID-19 can differ, for example between men and women. Many of the new COVID-19 vaccines are based on novel delivery methods, such as viral vectors or messenger RNA molecules. Clearly these are very effective in their delivery of rapid protection. But quite how well they will activate memory B cells and LLPCs, imparting long-lived immunity, remains to be seen.

 

By: Senior Lecturer in Biomedical Sciences, Brunel University London

Source: Why do antibodies fade after a COVID-19 infection, and will the same thing happen with vaccines?

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New data suggest it may be vaccine or bust. Get more medical news analysis at https://www.methodsman.com or https://www.medscape.com -~-~~-~~~-~~-~- You might be interested in my latest video: “Thanksgiving in the Coronavirus Era – Just Don’t Do It” https://www.youtube.com/watch?v=mNuvw…
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Scientists in China believe new drug can stop pandemic ‘without vaccine’

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A Chinese laboratory has been developing a drug it believes has the power to bring the coronavirus pandemic to a halt.The outbreak first emerged in China late last year before spreading across the world, prompting an international race to find treatments and vaccines.

A drug being tested by scientists at China’s prestigious Peking University could not only shorten the recovery time for those infected, but even offer short-term immunity from the virus, researchers say. Sunney Xie, director of the university’s Beijing Advanced Innovation Center for Genomics, told AFP that the drug has been successful at the animal testing stage.

“When we injected neutralizing antibodies into infected mice, after five days the viral load was reduced by a factor of 2,500,” said Xie.”That means this potential drug has (a) therapeutic effect.”The drug uses neutralizing antibodies—produced by the human immune system to prevent the virus infecting cells—which Xie’s team isolated from the blood of 60 recovered patients.

A study on the team’s research, published Sunday in the scientific journal Cell, suggests that using the antibodies provides a potential “cure” for the disease and shortens recovery time.Sunney Xie, director of the Beijing Advanced Innovation Center for Genomics, told AFP that the drug has been successful at the animal testing stage

Xie said his team had been working “day and night” searching for the antibody.”Our expertise is single-cell genomics rather than immunology or virology. When we realised that the single-cell genomic approach can effectively find the neutralising antibody we were thrilled.”

He said he hopes that the drug will be ready for use later this year and in time for any potential winter outbreak of the virus, which has infected 4.8 million people around the world and killed more than 315,000.”Planning for the clinical trial is underway,” said Xie, adding it will be carried out in Australia and other countries since cases have dwindled in China, offering fewer human guinea pigs for testing.

“The hope is these neutralizing antibodies can become a specialized drug that would stop the pandemic,” he said.China already has five potential coronavirus vaccines at the human trial stage, a health official said last week.But the World Health Organization has warned that developing a vaccine could take 12 to 18 months. Sunney Xie said his team had been working “day and night” on the new drug.

Scientists have also pointed to the potential benefits of plasma—a blood fluid—from recovered individuals who have developed antibodies to the virus enabling the body’s defences to attack it.

More than 700 patients have received plasma therapy in China, a process which authorities said showed “very good therapeutic effects”.”However, it (plasma) is limited in supply,” Xie said, noting that the 14 neutralizing antibodies used in their drug could be put into mass production quickly.

Prevention and cure

Using antibodies in drug treatments is not a new approach, and it has been successful in treating several other viruses such as HIV, Ebola and Middle East Respiratory Syndrome (MERS). Xie said his researchers had “an early start” since the outbreak started in China before spreading to other countries.

Ebola drug Remdesivir was considered a hopeful early treatment for COVID-19—clinical trials in the US showed it shortened the recovery time in some patients by a third—but the difference in mortality rate was not significant.More than 100 vaccines for COVID-19 are in the works globally. The new drug could even offer short-term protection against the virus.

The study showed that if the neutralising antibody was injected before the mice were infected with the virus, the mice stayed free of infection and no virus was detected.This may offer temporary protection for medical workers for a few weeks, which Xie said they are hoping to “extend to a few months”.

More than 100 vaccines for COVID-19 are in the works globally, but as the process of vaccine development is more demanding, Xie is hoping that the new drug could be a faster and more efficient way to stop the global march of the coronavirus.

“We would be able to stop the pandemic with an effective drug, even without a vaccine,” he said.

By Qian Ye and Matthew Knight

Source: https://medicalxpress.com

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